Visible-light-responsive reduced graphene oxide/g-C3N4/TiO2 composite nanocoating for photoelectric stimulation of neuronal and osteoblastic differentiation

Restoration of nerve supply in newly formed bone is critical for bone defect repair. However, nerve regeneration is often overlooked when designing bone repair biomaterials. In this study, employing graphitic carbon nitride (g-C3N4) as a visible-light-driven photocatalyst and reduced graphene oxide (rGO) as a conductive interface, an rGO/g-C3N4/TiO2 (rGO/CN/TO) ternary nanocoating with photoelectric conversion ability was fabricated on a Ti-based orthopedic implant for photoelectric stimulation of both bone and nerve repair. Compared with g-C3N4/TiO2 (CN/TO) and TiO2 nanocoatings, the ternary nanocoating exhibited stronger visible-light absorption as well as higher transient photocurrent density and open circuit potential under blue LED exposure. The improved photo-electrochemical properties of the ternary nanocoating were attributed to the enhanced separation of photogenerated carriers at the heterointerface. For the tested nanocoatings, introducing blue LED light irradiation enhanced MC3T3-E1 osteoblastic differentiation and neurite outgrowth of PC12 cells. Among them, the rGO/CN/TO nanocoating exerted the greatest enhancement. In a coculture system, PC12 cells on the ternary nanocoating released a higher amount of neurotransmitter calcitonin gene-related peptide (CGRP) under light irradiation, which in turn significantly enhanced osteoblastic differentiation. The results may provide a prospective approach for targeting nerve regeneration to stimulate osteogenesis when designing bone repair biomaterials.

Automated summary

Restoration of nerve supply is crucial for bone defect repair, but often overlooked in the design of bone repair biomaterials. In this study, a ternary nanocoating with photoelectric conversion ability was developed for photoelectric stimulation of both bone and nerve repair. The nanocoating exhibited improved photo-electrochemical properties and enhanced osteoblastic differentiation and neurite outgrowth under blue LED exposure. The findings suggest that this nanocoating could be a promising approach to target nerve regeneration for stimulating osteogenesis in bone repair biomaterial design.